1. Field of the Invention
The invention relates to substrate processing chambers. More particularly, the invention relates to calibration systems to calibrate adjustable nozzles in spin-rinse-dry systems.
2. Description of the Prior Art
Sub-quarter micron multi-level metallization is one of the key technologies for the next generation of ultra large scale integration (ULSI). The multilevel interconnects that are very important for this technology require reliable metallization and planarization of interconnect features. These features include contacts, vias, conductive lines, etc.
Aluminum and its alloys have been traditionally used to form features in semiconductor processing because of its high conductivity, its superior adhesion to silicon dioxide, its ease in patterning, and the ability to obtain it in a highly pure form. However, with the increase in circuit densities, copper is becoming a choice metal for filling sub 0.25 xcexcm, high aspect ratio interconnect features on semiconductor substrates. Copper and its alloys have lower resistivities than aluminum as well as a higher electromigration resistance. These characteristics are important for supporting the higher current densities experienced at high levels of integration and increased device speed associated with the newer semiconductor devices.
Despite the characteristics of copper that make its use desirable for semiconductor device fabrication, there are limited alternative processes for depositing copper into very high aspect ratio features. Thus, improvements in electroplating processes as applied to substrate manufacturing are being explored, especially as applied to high aspect ratio features of substrates.
Spin-rinse-dry systems (SRD) are used in conjunction with electroplaters and other devices, and are often used to chemically remove deposits (using etchant fluids) from undesired locations of the surface of substrates following processing. SRD systems are applicable to wet processes (such as electroplating) in which a liquid such as electrolyte solution is applied to the substrate. The SRD systems also can remove dried chemicals from a surface of the substrate following electroplating. Removing these dry chemicals is desired because they may interfere with the desired layering uniformity, adhesive capabilities, effectiveness of the processing, or simply may provide an undesired surface finish. The SRD systems typically then spin at least one substrate at a time at sufficient angular velocities to remove remaining fluid droplets by centrifugal force.
FIG. 1 is a partial cross section of an edge of a substrate 2 with one embodiment of layers deposited thereupon by successive processes, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and/or electroplating. The substrate 2 comprises an edge profile 6 that typically has a first bevel 8 adjacent a front side 12 and a second bevel 10 adjacent a backside 14. Doped regions 15 electrically connect to a feature 20 (such as a contact as shown) to form a portion of the circuitry of a semiconductor device. A dielectric layer 16 is deposited on the base 4 and is etched to form desired features, such as, for example, over the doped regions 15. A barrier layer 18, comprising Ti, TiN, Ta, TaN, and other known material is deposited over the dielectric layer 16. The barrier layer 18 reduces migration and diffusion of elements between adjacent layers and provides good adhesion of subsequent metal layer(s) to the dielectric 16. A conductive layer 21, typically copper, is deposited over the barrier layer 18, such as by electroplating, and fills the apertures and voids to form the interconnects between the layers.
Certain layers are not uniformly deposited around the edge profile to the backside 14 of the substrate. For example, the barrier layer 18 thickness reduces until it vanishes at merge point 17 thus permitting the conductive layer 21 to directly contact the underlying dielectric layer 16. The material of the conductive layer 21 at those locations where there is no barrier layer may diffuse into both the dielectric layer 16 and the silicon of the substrate 2, or vice versa. Such diffusion leads to xe2x80x9cpoisoningxe2x80x9d of the semiconductor device. This poisoning of the device results in unpredictable operation of the device. Furthermore, some undesired backside deposits 22 may form on the backside 14, further increase the possibility of unwanted diffusion between these adjacent layers. In copper electroplating, the copper has a high diffusion capability and also can poison the device. This unwanted deposition can adversely affect the performance gains achieved using copper. It is preferred to remove this copper or other unwanted materials from the backside or from other surfaces where it may have been deposited.
FIG. 2 is a partial cross section representing a desired deposition profile on the substrate 2. A portion of the deposited material (particularly the deposited material around the edge and backside 14) shown and described above in FIG. 1 is shown removed in FIG. 2. The dielectric layer 16, the barrier layer 18, and the conductive layer 21 each terminate a distance from the edge of the substrate 2 to form an edge exclusion zone 6a. In physical vapor deposition (PVD) and chemical vapor deposition (CVD) processing, which are conventionally dry processes, the ability to define the edge exclusion zone 6a is well known and is provided, for example, by use of clamp rings, shadow rings, and purge gases. This exclusion region prevents the formation of the deposition layer on the bevel, where it is easily flaked off. Electroplating typically requires the inclusion of a conductive layer in the exclusion region, to which power is applied to bias the substrate to attract ionic metal (typically copper) thereto to form the electroplated layer. This layer is typically an extension of a copper seed layer deposited over the face or field of the substrate prior to electroplating deposition.
However, this material must be removed from the edge, side, and back to allow the formation of edge exclusion zone 6a as shown in FIG. 2 after electroplating. The edge is complete to exclusion zone 6a typically extends from about 1 mm to about 3 mm or more along the upper surface 12 of substrate 2. In further processing, providing an edge exclusion zone 6a shown in FIG. 2 reduces the likelihood of the edge deposits being dislocated from the substrate 2, thereby contaminating the substrates 2. There is also less likelihood of unwanted diffusion through the layers. In processing, it may be desired to provide an edge exclusion zone along the upper surface 12 which is a surface in such processes as PVD or CVD over which the substrate 2 can be clamped or shadowed. It is desirable to limit deposits applied to such an exclusion zone since some of the deposits can be removed during processing, thereby possibly contaminating the substrates.
The fluid in many prior art SRD systems is applied to the substrate in the form of a fluid stream. A robot assembly as generally known in the art is used for the transporting of wafers to or from the SRD chamber. In many SRD systems, nozzles are used to adjust a location where the fluid stream impinges upon the upper and the lower surfaces of the substrate.
Nozzles in SRD systems can often be adjusted to alter the location where the fluid stream impinges on the substrate and the angle that the fluid stream is applied to the substrate. Accurate adjustment of the nozzle is desirable to ensure adequate coverage of an entire upper or lower surface of the substrate by the fluid applied by the fluid stream. There is typically a relatively small surface area upon the substrate that the fluid stream can impinge upon such that the fluid covers the entire surface of the substrate. Calibration is the process of adjusting the nozzles to provide suitable coverage.
Unfortunately, the calibration of adjustable nozzles is quite sensitive. As such, the adjustable nozzles may become misaligned during shipping, normal use, or inadvertent contact. However if the fluid stream does not impinge as desired upon the substrate, which may occur if the nozzle is knocked out of alignment and/or is not calibrated, then desired portions of the substrate may not be covered adequately by the fluid stream. Alternatively different surfaces of the substrate may be non-uniformly rinsed, thereby failing to adequately remove the deposits or dried chemicals as desired. While repositioning the adjustable nozzles is not difficult in itself, calibrating the adjustable nozzles properly such that the nozzle is directed at a desired location on the substrate whereby the fluid completely rinses the entire substrate is challenging.
Therefore, a need exists in the art for a system in which the adjustable nozzles in a spin-rinse-dry systems that can be inexpensively and repeatedly calibrated such that the adjustable nozzles apply fluid substantially uniformly over the entire surface of the substrate.
In one aspect, a spin-rinse-dry chamber comprises an adjustable nozzle. A calibration element may be positioned in the spin-rinse-dry chamber at which the adjustable nozzle may be directed. Targets (for example cross-hairs in one embodiment) may be located on the calibration element at a position corresponding to where it is desired to direct a fluid flow from the adjustable nozzle.
Another aspect provides a method of calibrating a spin-rinse-dry chamber having an adjustable nozzle comprising inserting a calibration element having a similar contour as a substrate into the spin-rinse-dry chamber. Fluid is then directed through the adjustable nozzle at a selected target position located on the surface of the calibration element.
The present invention is particularly applicable to spin-rinse-dry chambers to remove deposits or chemicals after electroplating processes have been applied to substrates.